(a) Field of the Invention
The present invention relates generally to a liquid crystal display (“LCD”) and a driving device of the same. More particularly, the present invention relates to an LCD having improved visibility and a driving device of the same.
(b) Description of the Related Art
Generally, an LCD includes a pair of panels individually having electrodes on their inner surfaces, and a dielectric anisotropy liquid crystal layer interposed between the panels. In the LCD, the variation of the voltage difference between the field generating electrodes, i.e., the variation in the strength of an electric field generated by the electrodes, changes the transmittance of the light passing through the LCD, and thus desired images are obtained by controlling the voltage difference between the electrodes.
However, the viewing angle of the LCD may not as wide as desired. Accordingly, various methods to overcome such a drawback have been developed in the field of LCDs. The most conspicuous one among recently proposed methods to ensure a wide viewing angle is the method of aligning liquid crystal molecules perpendicularly to upper and lower panels, and forming an aperture pattern or projection pattern in the field generating electrodes.
In particular, the aperture pattern formation method utilizes a fringe field that occurs near the apertures formed in the pixel electrodes and the common electrode. That is, the fringe field controls tilt directions of the liquid crystal molecules to ensure the wide viewing angle.
The projection forming method utilizes projections formed on the pixel electrodes and the common electrode of the upper panel. These projections distort an electric field generated between the two electrodes, so that tilt directions of the liquid crystal molecules are controlled.
In another method, apertures are formed in the pixel electrodes of the lower panel and projections are formed on the common electrode of the upper panel. The fringe field caused by the apertures and projections controls tilt directions of the liquid crystal molecules, thereby forming a multi-domain structure to ensure the wide viewing angle.
In multi-domain LCDs, a 10:1 contrast ratio-based viewing angle, or a gray scale conversion-based viewing angle defined as a critical angle of luminance conversion between the gray scales, is more than 80 degrees in all directions. In spite of such a good characteristic, the LCDs exhibit poor visibility at left and right sides of the screen due to a disagreement between a gamma curve at the front and a gamma curve at the side. For example, in a patterned vertically alignment (“PVA”) mode LCD, where an aperture pattern is formed in the common electrode in order to form a multi-domain structure, the luminance of the screen becomes higher and the color becomes closer to white as a viewing point moves to a side of the screen from a front center. In more excessive cases, intervals between the grayscales become too narrow, so that images may be dully expressed.
Recently, concern about the visibility of an LCD has increased due to the increasing use of LCDs in multimedia fields for enjoying moving pictures and still images.